Taxonomy term

february 2018

Genetics studies have dated the largest migrations of early Homo sapiens out of Africa to between 70,000 and 55,000 years ago, although smaller groups may have left earlier. The most widely accepted exodus theory, known as the “green carpet” or “green Sahara” hypothesis, holds that people likely left during wetter periods in the Sahara and Arabia, which would have allowed easier passage into Eurasia via the Middle East. But new research supports the opposite idea: that drier conditions may have triggered at least some of the exodus.

Sensitive instruments installed on and near the slow-moving landslide in Maca, Peru, have allowed scientists to observe the response of the landslide to earthquakes: information that can help researchers predict hazards from other slow-moving landslides in the region and perhaps around the world. But scientists are wondering whether the findings could also shed light on the triggering of fast-moving landslides by earthquakes.

A massive landslide has been encroaching on the village of Maca, Peru, since the 1980s. Today, it provides geologists with a laboratory to study slow-moving landslides, especially how they react to rainfall and earthquakes.

When geologists think of alabaster, they likely envision blocks of gypsum, its main mineral constituent; when art historians hear the word, statues crafted from the soft rock may come to mind. A new study focused on the sources of centuries-old alabaster artworks has geologists thinking about art history, and art historians pondering geochemistry. In the study, published in Proceedings of the National Academy of Sciences, researchers used isotope fingerprinting along with historical records to tie medieval and Renaissance alabaster sculptures to the quarries from which their materials were excavated.

All animals depend on their ecosystems for habitat. And, in turn, many animals impact their ecosystems by engineering the landscape to suit their needs. Beavers provide an iconic example of ecosystem engineering when they build dams, which influence streams and wetlands. The engineering efforts of salmon, meanwhile, can even shape the bedrock of the watersheds in which they live, according to a recent study that modeled the evolution of those watersheds over several million years.

Earth in the Hadean Eon, between 4.56 billion and 4 billion years ago, was much too hot to support active plate tectonics as we know it today, where cold, established plates slowly march around Earth. Yet some evidence, including from tiny zircon crystals dating to the Hadean, has suggested that a form of plate tectonics was active by about 4.1 billion years ago — about a billion years before many researchers think modern plate tectonics started. The mechanisms that could have initiated and sustained early tectonics are unclear, but according to a new study, constant bombardment of early Earth by meteorites could have triggered temporary bursts of early tectonism.

Burning coal releases carbon dioxide, which warms the planet when the gas escapes into the air. On the flip side, coal formation sequesters carbon dioxide removed from the atmosphere by plants, which contributes to global cooling as the planet’s greenhouse gas blanket thins. According to new research, so much carbon was removed from the atmosphere in the Carboniferous Period, when most of Earth’s coal reserves formed, that the planet became almost completely covered in ice.

Greenland’s 1.7-million-squarekilometer ice sheet is shrinking. But how much meltwater and sediment drains from the ice sheet through rivers? Researchers are studying the island’s deltas to find out, and are getting help from some longforgotten aerial photos taken by the Danish Air Force in the 1930s.

During the Pleistocene, saber-toothed cats were formidable predators, with their massive canines and powerful front legs sporting razor-sharp claws. The bones of saber-toothed cats are thicker and more robust compared to those of other large cats, both modern and extinct. And previous studies of Smilodon have shown that their forelimbs in particular featured several adaptations, including thickened cortical bone, which would have increased strength, presumably useful in subduing ambushed prey.

Canada’s Burgess Shale is famous for a wide array of exquisitely preserved 500-million-year-old fossils, which are found in a dozen localities in the Canadian Rockies. Linking all these localities today is a geologic feature called the Cathedral Escarpment, which formed in the Cambrian as a steep line of underwater cliffs where regular mudslides are thought to have gently buried a diversity of organisms, setting the stage for the prolific fossil beds. However, new mineralogical clues found at several of the fossil-rich sites suggest that mud volcanism may have also played a starring role in creating the Burgess Shale.